The present technology relates to tools for measuring and analyzing the orientation of a toric lens, or other lens not radially symmetric, disposed on a patient's eye or other element on which the lens is disposed, and for modifying specifications for the lens based on the measurement.
A problem arises when fitting a contact lens for a patient when the lens is not radially symmetric. In particular, a lens that is not radially symmetric, such as a toric lens, is designed to be oriented at a specific angle relative to the eye. However, when placed on the eye, the lens may rotate to an angle of repose on the eye that varies from eye to eye. If the angle of repose is sufficiently different than the specified angle for the lens, then the lens will be ineffective or uncomfortable for the wearer.
One of the steps in fitting asymmetric lenses is to determine whether the lens rotates on the eye and the amount of rotation. Eye care professionals (ECP) have used an expensive special instrument known as a slit lamp to determine the angle of repose of the lens on a patient's eye. Toric lenses, for example, typically have an index mark on the lens outside the optic region that can be viewed using the slit lamp, as an indication of the angle of repose. The ECP can estimate the angle of repose based on the location of the index mark, and make adjustments to the specification for the lens. A slit lamp, however, is expensive and requires specialized training. It is desirable, therefore, to provide an easy to use technology to measure and analyze the orientation of lenses on eyes.